1. Field of the Invention
The present invention relates to a liquid crystal display device and, more particularly, to a liquid crystal display device of active matrix type using thin film transistors or the like.
2. Prior Art
In a liquid crystal display device of active matrix type, non-linear device (e.g., switching devices) are disposed in a manner to correspond to a plurality of pixel electrodes arranged in matrix, respectively. The liquid crystal in each pixel is always drive, in principle, (at a duty ratio of 1.0). In comparison with the so-called xe2x80x9csimple matrix typexe2x80x9d which employs a time division driving system, therefore, the active system has better contrast and has become an indispensable technique particularly in a color liquid crystal display device. A typical example of the switching devices is a thin film transistor (TFT).
A liquid crystal display circuit (or a liquid crystal display panel) is constructed: by superposing a lower substrate, which is formed, over a lower transparent glass substrate with reference to a liquid crystal layer, sequentially with a thin film transistor, a transparent pixel electrode, a passivation film for the thin film transistor, and a lower orientation film for orienting liquid crystal molecules; and an upper substrate, which is formed over an upper transparent glass substrate sequentially with a black matrix, a color filter, a passivation film for the color filter, a common transparent pixel electrode and an upper orientation film, such that their orientation films are opposed to each other; by bonding the two substrates by a sealing material arranged around the edges of the substrates; and by sealing up the liquid crystals between the two substrates. Incidentally, a back light is arranged at the side of the lower substrate.
Here, the liquid crystal display device of active matrix type using the thin film transistors is known in Japanese Patent Laid-Open No. 309921/1988 or on pp. 193 to 210 of Nikkei Electronics entitled xe2x80x9cActive Matrix Type Color Liquid Crystal Display of 12.5 Type Adopting Redundant Constructionxe2x80x9d and issued on Dec. 15, 1986 by NIKKEI McGRAW-HILL, for example.
Since a shield casing made of a metal plate or a liquid crystal display circuit is fixed by means of rivets, the liquid crystal display device of the prior art is troubled by a difficulty in repair or replacement of the back lights.
An object of the present invention is to provide a liquid crystal display device which can be easily repaired or repaired in its back lights.
According to one embodiment of the present invention, there is provided a liquid crystal display device which comprises: a shield casing made of a metal plate and having fixing pawls and fixing hooks; an middle frame for holding a liquid crystal display; and a lower casing for packaging back lights, wherein the fixing pawls of said shield casing are bent in corresponding recesses formed in the middle frame, and wherein the fixing hooks of said shield casing are fitted on corresponding projections formed on the lower casing.
The liquid crystal display device can be easily repaired and replaced in its back lights because the fixing pawls and hooks of the shield casing can be easily removed and because the shield casing, the middle frame for holding the liquid crystal display and the lower casing for packaging the back lights are easily assembled and disassembled.